Background Alexander et al5,7-9 proposed that the basal ganglia and thalamus participate in five parallel segregated circuits with selected cortical areas in the frontal lobe. Two of these circuits are related to motor function, and influence skeletomotor and oculomotor areas of cortex. The remaining three loops are connected with nonmotor areas in the frontal lobe, including the dorsolateral prefrontal cortex, the lateral orbitofrontal cortex, and the anterior cingulate/medial

orbitofrontal cortices. These frontal regions are known to be Inhibitors,research,lifescience,medical involved in aspects of planning, working memory, rule-based learning, attention, and emotional regulation such as the decision threshold in reaction time tasks or in the control of automatic Inhibitors,research,lifescience,medical visuospatial

attention.10-42 Basal ganglia functional connectivity, based on a recent meta-analysis of 126 positron emission tomography (PET) and fMRI imaging publications, showed that patterns of functional connectivity between the cortex and the striatal nuclei are broadly consistent with the predictions of this classical parallel loop model.13 The frontal lobe may be viewed as comprising two distinct anatomical Inhibitors,research,lifescience,medical and functional systems, reflecting its dual developmental origin.14 The sequential processing of sensory, spatially related, and motivational Inhibitors,research,lifescience,medical information is mediated by a dorsal system, which involves dorsolateral and medial portions of the frontal lobes, interconnected with the posterior parietal lobe and cingulate gyrus. Emotional tone is mediated by a second, ventral system, which involves the orbital surface of the frontal lobes. The function of

the frontal lobes as an integrator of infermation, related both to the external sensory and internal limbic worlds and its role in motivation and appropriate nections Inhibitors,research,lifescience,medical critically important to an understanding of both normal and disordered psychomotor functions. The architectonic organization of the prefrontal cortex is reflected in the pattern of prefrontostriatal projections.15,16 The dorsal architectonic trend, which originates before in the rostral cingulate gyrus and culminates in the dorsal portion of the frontal eye field, maps onto the dorsal caudate nucleus. In contrast, the ventral architectonic trend, which originates in the ventral orbital region and culminates in the ventral portion of the frontal eye field, maps onto the ventromedial portion of the caudate and the adjacent portion of the nucleus accumbens. Cortical areas that are closely connected functionally appear to send converge ing projections into adjacent regions of the striatum.17-20 Information derived from the cortex is recombined at the striatal level to form small, functionally find more specialized domains.